DRAFTING
New:
– Aerial insect populations in the Halifax Backlands and prey availability to the Common Nighthawk (Chordeiles minor)
Honors Biology thesis by Siobhan Herold, Dalhousie University 2025, 69 p (2.4 MB PDF)
ABSTRACT Insects are experiencing rapid and dramatic global declines associated with human activities such as agricultural intensification, urbanization and pollution. Drastic loss of insects impairs essential ecosystem functions and services, including food provision for many predators, most notably aerial insectivores, a guild of animals that feed exclusively on insects. Here I focus on the spatiotemporal changes in insect abundance and its possible effects on the Common Nighthawk (Chordeiles minor), a migratory, ground-nesting nightjar and Species at Risk in Canada. As an aerial insectivore, insect declines are hypothesized to be one of the leading threats to this species. Observations of the nighthawk in the Halifax Backlands, a suburban wilderness area near Halifax, Nova Scotia, suggest this area hosts important nesting and foraging grounds for this species in Atlantic Canada. Malaise intercept traps and insect light traps were deployed at 21 sites across the Backlands in the summer of 2024 to investigate aerial insect populations in the area. Insect samples were sorted into orders, counted and dried to obtain dry biomass. Insect sample diversity varied between trap types and across sites. Biomass of insect prey > 5 mm did not correlate with nighthawk activity sampled acoustically with autonomous recording units (ARUs). A generalized linear mixed model suggested that insect abundance was greatest in areas with low nighthawk activity, but a generalized linear model indicated nighthawks may travel to sites daily to exploit high insect abundance. Temperature was found to be the best predictor for insect abundance over time, while lunar percentage affected abundance and biomass in light traps samples. No significant difference in insect biomass across sites suggests that nighthawks may opt to forage in areas with lower overall abundance but target larger prey. Important nighthawk foraging areas include north and central regions of the Backlands, but the data did not suggest that nighthawks foraging or breeding habitat choices were driven by insect abundance.
– Spatial Ecology of the Common Nighthawk (Chordeiles minor) in the Halifax Backlands
Honors Biology thesis by Madeleine Kurtz, Dalhousie University 2025, 70 p (14 MB PDF)
ABSTRACT Located in southern Halifax, NS, the Halifax Backlands is a suburban wilderness that is home to a diversity of species and ecosystems, including the Common Nighthawk (Chordeiles minor). The Common Nighthawk is a migratory aerial insectivore that is classified as Special Concern under Canada’s Species at Risk Act. This study aimed to determine the spatial distribution of Common Nighthawks within the Halifax Backlands and investigate the influence of environmental characteristics on this distribution. Furthermore, seasonal and diurnal trends in Common Nighthawk activity were examined. Between May and September of 2024, Common Nighthawks were sampled in the Halifax Backlands using Autonomous Recording Units (ARUs) and visual surveys. Auditory recordings were analyzed using BirdNET. Auditory detections were plotted to visualize seasonal and diurnal trends in activity. Using location data collected during visual surveys, kernel density analysis was performed to ascertain spatial distribution. The importance of environmental variables on nighthawk spatial distribution was analyzed using a generalized linear model (GLM). The study found that Common Nighthawk activity was greatest in the northern portion of the Backlands, and that prey abundance, elevation, and bare ground were all influential in this distribution. Activity varied across the season, beginning in late-May, peaking in July, and ending in mid-September. Diurnal trends in activity showed similar trends spatially and seasonally, with peaks in activity during sunset and an hour before sunrise. Results of the study are important for improving understanding of the spatial ecology of Common Nighthawks in Atlantic Canada, and can inform future monitoring and conservation strategies in the Halifax Backlands.
Related
– Listening for the elusive nighthawk in the Purcells Cove Backlands
Chris Lambie for Saltwire/PNI Atlantic, Dec 27, 2023 Some extracts:
The search for the elusive nighthawk in the Purcells Cove Backlands has produced a rare recording of a mating pair with their offspring.
And the folks who aim to limit development of the 1,350-hectare wilderness area between Purcells Cove Road and Herring Cove Road hope to produce more research next spring and summer to prove it is home to more common nighthawks , a species at risk in Nova Scotia.
We spot them. But they are … elusive. So, you see them way up high in the air catching insects and it’s at dusk or it’s at dawn,” Martha Leary, a director of the non-profit Williams Lake Conservation Company, said Wednesday.
This past August, Leary contacted Cindy Staicer, a retired Dalhousie University biologist, who agreed to loan an autonomous recording unit to a small group of volunteers who wanted to learn more about nighthawks in the backlands.
“We identified five sites in the backlands that we thought were possible areas where they might hang out, where they might nest, where they might call their territory,” Leary said.
They programmed the borrowed device to record for three hours at dawn and dusk.
“What we found was that there were certain areas that were real hot spots,” Leary said. “There were recordings that showed that there would be three nighthawk voices in an area — which means that’s a nest. It means that there’s a pair and that there’s an offspring. That’s really, really exciting.”
Staicer analyzed their recordings. “She was really encouraged,” Leary said. “To find that there was evidence of breeding nighthawks within a 10-minute (drive) — or perhaps an hour-long walk — from downtown Halifax, was very exciting to her as well.”
– Ground-nesting Birds 2024: Common Nighthawk
By The Bird Team: Joshua Barss Donham, Fulton Lavender, Cathy Smalley, Katie Studholme. Video by Joshua Barss Donham
“Nighthawk numbers have been in steep decline. It is a Species of Concern Nationally, and a Species At Risk in Nova Scotia, and thereby legally protected under the NS Endangered Species Act.
The Backlands is a special place where they are surviving and raising their young. Just coincidentally (or not), the Common Nighthawk was recently designated Halifax’s Bird of the Year! (View post June 29, 2024)
How can you tell when the Nighthawks are back in the Backlands? Listen at dawn and dusk for their characteristic buzzy “peent” calls, and look up for the swooping, looping feeding flight of these remarkable birds.
Nighthawk at dusk in mid summer 2023 Video by Joshua Barss Donham